A wide variety of versatile motorized devices are used in a wide variety of industries, such as the construction, maintenance, farming and landscaping industries. Such devices include skid steer loaders, light tractors, “four-wheeler” all terrain vehicles and other compact power units. Skid steer loaders, in particular, are known to be useful and versatile in the handling of a variety of materials, including earth moving and material transportation tasks. One-line of skid steer loaders is sold under the trademark Hydra-Mac™, manufactured by Hydra-Mac International Inc., of Thief River Falls, Minn. Another line of skid steer loaders is sold under the trademark Gehl™, by the Gehl Company, West Bend, Wis.
Skid steer loaders are particularly useful due to their compact size and maneuverability. However, one problem associated with using such loaders, is that they have a tendency to be somewhat unstable when loaded or when going up or down inclines, especially as the angle of the incline increases. For example, particularly for higher weight loads, the loader tends to tip forward upon lifting such a load, especially if the loader is facing down an incline. Should the loader be facing up an incline, the higher a heavy weight load is lifted, the loader experiences a tendency to tip backwards. This tipping tendency further reduces the efficient use of such loaders as an operator is limited in the amount of weight that can be lifted and safely transported, thus requiring longer time periods to accomplish the same work product. Further, there are incline angles that current skid steer loaders are simply incapable of traversing.
Other use problems experienced with such loaders includes a bouncing action that reduces operator comfort and operational efficiency, effects particularly experienced when driving over an uneven surface, especially when carrying a load, and insufficient traction when using an attachment on the loader such as a bucket or a blade to dig or push material.
Various means have been employed to overcome these problems. Counterweights may be used at the opposite end of the power unit from the load lifting attachment to balance the loader. Though this may help with reducing the tendency of a loader to tip forward, it only increases the tendency to tip backward. Load stabilizers have been used which are incorporated to the front end of a skid steer loader in the area of an attachment to the loader, examples of which are disclosed in U.S. Pat. No. 6,551,050 and published U.S. Patent application No. 2003/0108413. However, such load stabilizers impede the effective use of the skid steer loader to dig or push materials, where such actions involve or create different surface grade levels or when attempting to use a skid steer loader to product a level grade from an undulating grade. Caster assemblies have been used which are incorporated to the rear end of a skid steer loader, an example of which is disclosed in U.S. Pat. No. 6,439,332. Though engagement of the caster assembly may provide some bounce control when carrying an object at the front of a skid steer loader, engagement of the caster assembly reduces the transfer of power to ground engagement by lifting two of the driven wheels off of the ground surface.
Thus improvements to the versatile skid steer loader that enable more efficient work output through greater transfer of power to ground engagement, that enable safe and efficient transit of steeper inclines and that provides for greater operator safety through more comfortable ground transit operation and greater stability on inclines, is needed.